Drill strings, used in drilling wells, comprise drilling and well tools attached to sections of drill tubing. As the string is lowered into the well, additional sections of tubulars are added to extend the string's length. These sections of pipe are connected via threaded sections on each end, sometimes referred to as “pin” and “box,” representing the male and female portions of the pipe section. The drill string is held in place while the new section of pipe is rotated into connection with the next pipe. Likewise, tubular sections may be removed by rotating the pipe section in reverse.
Connection and disconnection of drill string tubulars is typically accomplished by a mechanical device such as an iron roughneck. A power tong device is used to rotate the section of pipe. A typical power tong will employ low torque, high speed rotation of the pipe up until full connection with the next pipe. Then the tong will shift into a low speed, high torque setting to complete the mating. By the same vein, when removing pipe, power tongs use the high torque setting to break the joint, and then shift into high speed, low torque rotation to unthread the tubular.
Power tongs must sufficiently grip the tubular section before applying torque. Hydraulic gripping systems located within the rotating portion of a power tong require rotary seals to transfer fluid from the fixed portion of the tong to the rotating portion. These rotary seals can sometimes leak and may wear out. It is therefore desirable to provide a power tong without rotary seals.